One of the best Dreamcast games ever made is Sonic Adventure, there's no denying it. It took the Sonic franchise to a new level, it was loved by many, and still is, so much so that gamers are still demanding a new remaster for modern consoles for both Sonic Adventure and Sonic Adventure 2.
YouTube channel Shacknews Interviews had a discussion with Sonic Team's lead Takashi Iizuka about Sonic Racing, but slipped in a question about Sonic Adventure remasters, asking if any will come to fruition anytime soon.
But unfortunately was met with a kind and respectful no.
When I think about what it would take to kind of bring that game up to the standards and expectations of what the modern gaming audience would want, I think it would be about as much time and energy as it would to make a new title. Part of me is thinking maybe I should just make a brand new title and that’s why there’s currently no plans.
Takashi Iizuka
It's a hard pill to swallow for sure, and it was met with a honest answer which is always appreciated, there's nothing worse than not answering something like this and keeping gamers excited for something that is not coming.
I think it's a smart move for SEGA to focus on future Sonic games as I have a thought that was mentioned in our video about retro gaming on the Nintendo Switch 2, that SEGA will bring classic Dreamcast games to Nintendo Switch Online.
I am not saying that's the reason why Sonic Adventure won't be remastered but its unlike SEGA to leave great games out of the gaming cycle. SEGA already has Genesis/Mega Drive games on NSO, and there's over 20 to choose from, so I believe its in their best iterests to do the same to their Dreamcast games.

Sonic needs all the attention it can get, Crazy Taxi is being remastered, Ecco The Dolphin remaster is in the works and so is a new Jet Set Radio. Adding these great games to NSO for new customers to explore just gives their upcoming games even more exposure.
That is why I believe they're not focused on the Sonic Adventure Remaster right now in its entirety, as they know its coming to Nintendo fans eventually in a NSO form.
But that's just my hunch!